Untitled Quiz

Cellular Form and Function

• Cytology is the scientific study of cells.
• All organisms are composed of cells and cell products.
• Cells are the simplest structural and functional units of life.
• Cells are alive.
• An organism's structure and functions are due to cell activities.
• Cells arise only from pre-existing cells.
• All life traces its ancestry to the same original cells.
• Cells of all species have fundamental similarities in their chemical composition and metabolic mechanisms.

Modern Cell Theory

• Cytology is the study of cells.
• All organisms are composed of cells and their products.
• Cells are the fundamental unit of structure and function of all living things.
• All living things come from preexisting cells.
• The cells of all organisms share fundamental similarities in their chemical composition and metabolic mechanisms.

Cells: Prokaryote vs Eukaryote

• Prokaryotic cells are simpler and smaller than eukaryotic cells.
• Prokaryotes are commonly known as bacteria, 10-100 microns in size and can be single-celled or filamentous (strings of single cells).
• Prokaryotic cells lack membrane-bound organelles.
• Eukaryotic cells are larger and more complex than prokaryotic cells.
• Eukaryotic cells have membrane-bound organelles and chromosomes.
• Eukaryotic cells can be multicellular.

Prokaryotic Cells

• Two groups: Archaebacteria and Eubacteria.
• Archaebacteria are recently discovered and live in extreme environments like salt lakes, hot springs, and deep in the ocean.
• Eubacteria are most common and well-studied species like Escherichia coli (E. coli), which inhabit soil and surface water.

Prokaryote Lifestyle

• Prokaryotes are unicellular. They exist as single individuals, as colonies forming a film, or as filamentous structures forming chains of cells.

Prokaryote Feeding

• Prokaryotes can be photosynthetic, obtaining energy from sunlight.
• Some are disease-causing, feeding on living organisms.
• Others are decomposers, feeding on dead organisms.

Eukaryotes

• Eukaryotic cells are larger and more complex.
• Eukaryotic cells have membrane-bound organelles.
• Eukaryotic cells contain chromosomes.
• Eukaryotic cells can be multicellular.
• Eukaryotes include animal and plant cells.

Organelles

• Organelles are membrane-bound cell parts within the cytoplasm.
• They act like mini-organs with unique structures and functions.

Animal Cell vs Plant Cell

• Plant cells have a cell wall, chloroplasts, and a large central vacuole, while animal cells have centrioles and lysosomes.

Viruses

• Viruses are parasites of cells.
• They replicate inside host cells, using the host's machinery to make more virus particles.
• They contain DNA or RNA surrounded by a protein coat (capsid).
• Outside of a host cell, a virus is a nonliving particle called a virion.

Cell Shapes

• Cell shapes vary greatly, including squamous, cuboidal, columnar, polygonal, stellate, spheroid, fusiform (spindle-shaped), and fibrous.

Microscopes

• Microscopes are used to view cells too small to see with the naked eye. Parts include an eyepiece, arm, objective lenses, stage clip, diaphragm, stage, coarse adjustment knob, fine adjustment knob, and base.

Cell Size

• Most human cells are 10-15 micrometers in diameter.
• Egg cells are much larger (100 μm).
• Nerve cells can be a meter long.
• Cell size is limited by the surface area-to-volume ratio. A larger surface area allows for more efficient nutrient absorption and waste removal.

Cell Structure

• All cells have three basic parts:
  • Plasma/Cell membrane (outer boundary)
  • Nucleus (DNA containing region)
  • Cytoplasm (semi-fluid substance between membrane and nucleus)

Cytoplasm

• Cytoplasm is the material between the plasma membrane and the nucleus.
• Cytosol is a largely watery substance containing dissolved proteins, salts, sugars, and other solutes within the cytoplasm.
• Cytoplasmic organelles are the metabolic machinery of the cell.

Nucleus

• The nucleus contains the nuclear envelope, nucleoli, DNA (as chromatin) and distinct compartments.
• It's the control center of the cell, containing the genetic library (DNA) and blueprints for proteins.
• It dictates the kinds and amounts of proteins to be synthesized.

Nuclear Envelope

• The nuclear envelope is a selectively permeable double membrane barrier containing pores.
• It encloses the jelly-like nucleoplasm containing essential solutes.
• The outer membrane is continuous with the rough ER and studded with ribosomes.
• The inner membrane is lined with the nuclear lamina which maintains the structure of the nucleus.
• The pore complex regulates transport of large molecules.

Nucleoli

• Nucleoli are dark-staining spherical bodies within the nucleus.
• They are the site of ribosome production.

Ribosomes

• Ribosomes are small granules of protein and RNA.
• They're found in nucleoli, cytosol, and on the outer surfaces of rough ER and the nuclear envelope.
• Ribosomes read coded genetic messages (mRNA) and assemble amino acids into proteins.

Endoplasmic Reticulum

• Rough endoplasmic reticulum (RER) is studded with ribosomes and functions in protein and phospholipid synthesis.
• Smooth endoplasmic reticulum (SER) lacks ribosomes; it plays a role in detoxification, steroid hormone synthesis, and lipid synthesis.

Golgi Apparatus

• The Golgi apparatus is a series of stacked and flattened membranous sacs called cisternae.
• It modifies, concentrates, and packages proteins.
• Transport vesicles from the ER fuse with the Golgi, and proteins then pass through the apparatus.
• Secretory vesicles leave the Golgi to travel to other parts of the cell.

Lysosomes

• Spherical membranous bags containing digestive enzymes.
• Digest ingested bacteria, viruses, and toxins.
• Break down nonfunctional organelles and useful tissue.
• Breakdown glycogen, releasing thyroid hormone.
• Breakdown bone, releasing calcium.

Peroxisomes

• Membranous sacs containing oxidases and catalases.
• Detoxify harmful or toxic substances.
• Neutralize dangerous free radicals.

Mitochondria

• Organelles specialized for ATP synthesis (energy currency of the body).
• Vary in shape (spheroid, rod-shaped, bean-shaped).
• Surrounded by a double membrane, the inner membrane containing folds called cristae.
• The space between the cristae is the matrix.

Chloroplasts

• Surrounded by two membranes and contain DNA.
• Some store starch or fats.
• Some contain pigments absorbing visible light
• (e.g. chlorophyll).
• Chloroplasts convert sunlight's energy into chemical energy.
• They contain stacks of thylakoids.

Cytoskeleton

• The cytoskeleton is the "skeleton" of the cell, a dynamic, elaborate series of rods running through the cytosol.
• It consists of microtubules, microfilaments, and intermediate filaments.

Cell Wall

• Plant cells have a cell wall outside the plasma membrane.
• Helps support and protect the plant cell.
• Composed of cellulose, which hardens the entire structure.
• Pores in the cell wall allow ions to pass into or out of the cell.

Other Cellular Structures

• Microvilli: Finger-like projections on the cell surface increasing absorptive surface area and play a sensory role.
• Cilia: Long, hair-like projections on the cell surface aiding in movement and having sensory roles.
• Flagella: Longer than cilia, usually solitary projections in some single-celled organisms. Functions in the movement of whole cells, such as sperm.

Differences Between Animal and Plant Cells

• Plant cells have chloroplasts, a cell wall, and a large central vacuole, but lack centrioles and lysosomes typically found in animal cells.
• Animal cells have centrioles and lysosomes commonly lacking in plant cells.

Plasma Membrane

• A very thin, oily film with various proteins embedded into its structure.
• Defines cell borders, controls material exchange with its environment, and governs interactions with other cells.
• Primarily constructed from a phospholipid bilayer of amphiphilic lipids.
• Also comprises proteins, which are embedded or attached to it.

Transport Mechanisms

• Plasma membrane acts as a barrier and a gateway between cytoplasm and extracellular fluid selectively allowing substances across it.
• Passive transport mechanisms use kinetic energy.
• Active transport mechanisms utilize ATP.
• Vesicular transport moves materials into or out of the cell encased within vesicles.

Passive Transport

• Passive transport mechanisms like diffusion, osmosis, and filtration don't require ATP.
• Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration across the cell membrane. Factors affecting diffusion rate include temperature, molecular weight, steeppness of the concentration gradient, surface area of the membrane, and membrane permeability.
• Osmosis is the net movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration
• Facilitated diffusion is the passive transport of molecules across the membrane using carrier proteins or channels.

Tonicity

• Tonicity refers to the ability of a solution (surrounding a cell) to cause a cell to gain or lose water.
• Hypotonic solution contains a lower concentration of solutes than the cell’s interior, causing the cell to gain water (and swell/lyse).
• Hypertonic solution contains a higher concentration of solutes than the cell’s interior, causing the cell to lose water (and shrink/crenate).
• Isotonic solution has the same solute concentration as the cell’s interior; no change in the cell. Typical saline solution is isotonic to blood cells.

Active Transport

• Active transport is energy-requiring. Carrier proteins are used to move substances across the cell membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration using ATP.

Vesicular Transport

• Vesicular transport is an active process employing ATP.
• Materials are moved into or out of the cell by enclosing them in vesicles. Endocytosis and exocytosis are types of vesicular transport.

Endocytosis

• Phagocytosis (cell eating) is the engulfing of large particles or other cells.
• Pinocytosis (cell drinking) is the ingestion of fluids or dissolved substances.
• Receptor-mediated endocytosis involves receptor proteins on the cell membrane binding specific target molecules, and they are then drawn into the cell by membrane deformation.

Exocytosis

• Exocytosis is the process in which materials are released from the cell via vesicles.
• These vesicles fuse with the plasma membrane to release their contents outside the cell. This mechanism can also replace plasma membrane that has been removed by endocytosis.